Hydrocracking process with reactivation of the catalyst



United States Patent Ofiice 3,132,091 Patented May 5, 1964.

3,132,001 HYDRDCRACKIN G PROCESS WITH REACTI- VATION OF THE CATALYST Dean Arthur Young, Yorba Linda, Calif., assignor to Union Oil Company of California, Los Angeles, Calif, a corporation of California No Drawing. Filed Sept. 26, 1960, Ser. No. 58,164

5 Claims. (Cl. 208-111) This invention relates to the catalytic hydrocracking of high-boiling hydrocarbons to produce therefrom lower boiling hydrocarbons, boiling for example in the gasoline range. The invention is directed specifically to certain novel methods for improving the overall activity of regenerated hydrocracking catalyst composed of a silicacontaining cracking base upon which is distended a hydrogenating component from the group consisting of nickel and cobalt. Briefly, the basic novel feature of the invention involves a catalyst regeneration technique, Wherein the deactivated catalyst is first subjected to an oxidation treatment to burn oii carbonaceous deposits and per-. haps other deactivating materials, and is then subjected to a' reduction treatment in the presence of both hydrogen and steam. It is found that when steam is added to the reduction gas, the catalyst is restored essentially to its initial fresh activity, whereas if dry hydrogen is used for the reduction, a considerably less active regenerated catalyst is obtained.

It is therefore a principal object of this invention to provide methods for regenerating nickelor cobalt-containing hydrocracking catalysts to restore essentially their fresh hydrocracking activity. The overall objective is to extend the total active lifeof the catalyst, and to obtain the most efiicient use thereof during its total life span. Other objectives will be more apparent from the detailed description which follows.

It is well known that composites of nickel and/or cobalt deposited upon silica-containing cracking bases are active hydrocracking catalysts. It is also well known that underhydrocracking conditionsthe activity of such catalysts declines gradually, the rate of deactivation depending to a large extent upon the severity of the hydrocracking conditions, and the feedstock employed. This deactivation is ordinarily not permanent, but is due at least largely to the deposition of combustible deposits upon the catalyst, e.g., coke, tars, sulfur, nitrogen compounds, and the like. When the catalysts have declined to an undesirably low level of activity, it is known that their activity may be restored to a considerable degree by combustion with oxygen-containing gases, which combustion is usually followed by a hydrogen reduction step.

-I have found that this conventional regeneration procedure does not restore the catalyst to its original activity, but usually only to about "70-90% of the original activity; It hasnow been discovered however that by adding steam to the reduction gas, the catalyst is restored to essentially its original activity. The theoretical explanation for this result is highly uncertain; it may for example be due to the combined effect of water and hydrogen upon the surface acidity of the cracking base, or it could be due to the specific reducing effect of the steam-hydrogen mixture upon the hydrogenating component of the catalyst. It is therefore not intended to limit the invention to any theoretical explanation of the observed phenomenon, but to the actual technique employed.

The regenerated catalysts of this invention may be employed for the hydrocracking of substantially any mineral oil fraction boiling above the conventional gasoline range, i.e., above about 300 F., and usually above about 400 F., and having an end-boiling-point up to about 1,000"

F., but preferably not greater than about 750 F. These feedstocks may be sulfur-free, or they may contain up to about 5% by weight of sulfur, in the form of organic sulfur compounds. They may also contain organic nitrogen compounds, but if nitrogen compounds are present, it is ordinarily necessary to utilize hydrocracking temperatures in the upper ranges hereinafter defined. Specific feedstocks contemplated comprise straight-run gas oils and heavy naphthas, coker distillate gas oils and heavy naphthas, deasphalted crude oils, cycle oils derived from catalytic or thermal cracking operations and the like. These feedstocks may be derived from petroleum crude oils, shale oils, tar sand oils, coal hydrogenation products and the like. Specifically, it is preferred to employ oils having an end-boiling-point between about 400 and 650 F., an API gravity between about 30 and 35, and containing at least about 30% by volume of acid-soluble components (aromatics plus olefins).

The catalysts of this invention comprise a major proportion of a solid refractory oxide cracking component including silica, plus a minor proportion, e.g., about 1 to 30% by weight of a hydrogenating component from the group consisting of nickel and cobalt. The exact chemical state of the hydrogenating component is not ordinarily ascertainable with accuracy, but will usually comprise a mixture of the free metal, the oxides, and/ or sulfides. Any of these chemical forms are active for hydrogenation to some degree. The cracking component on which the hydrogenating component is deposited may consist for example of synthetic coprecipitated silicaalumina, silica-zirconia, silica-titania, silica-titania-zirconia, silcia-alumina-zirconia, silica-magnesia, and the like. Acid activated montmorillonite clays may also be employed. Ordinarily, the silica content of the cracking base will be between about 20% and by weight. Any of these cracking bases may be further activated by the incorporation of small amounts, e.g., (LS-5% by weight, of acidic materials such as fluorine or chlorine.

. One particular class of cracking bases contemplated herein comprises a coprecipitated mixture of 10 to 65% silica, 15 to 65 titania, and 15 to 65 %zirconia. The composite cracking bases of these compositions are mildly acidic and are initially somewhat less active than the more highly acidic combinations such' as silica-alumina (containing between about 50% and 90% silica). But the more mildly acidiccracking bases such as silica-zirconia-titania, silica-zirconia, or silioa-titania, are more active in the presence of large, amounts of organic nitrogen compounds in the feed.

The hydrogenating component may be added to the cracking base by any of the conventional procedures, e.g., coprecipitation, impregnation, co-trit-uration, etc. Ordinarily, impregnation of the calcined cracking base with an aqueous solution of a decomposable salt of nickel or cobalt is preferred. Following the impregnation, the catalyst is drained, dried and calcined at e.g., 500-1,200 F. for 1 to 12 hours.

Hydrocracking conditions to be employed herein (either with the fresh catalyst or the regenerated catalyst) fall within the following ranges:

Hz/oil ratio, s.c.f 1, 000-15, 000 2, 000-10, 000 LHSV 0. 1-10 0. 5-5

Depending upon the severity of the hydrocracking conditions employed, and the refractoriness of the feed, it will be observed that the activity of the catalyst will have declined considerably after a period of time ranging between a few hours to several months. When the activity has declined to an uneconomic level, the flow of feedstock is terminated, and the catalyst container is purged with nitrogen or other inert gas to flush out volatilizable hydrocarbons, and then the. oxidation step is commenced. Since the oxidation is veryexothermic, care must be exerc'ised to avoid temperatures in excess of about 1,500 F., in that such high temperatures tend to irreversibly deactivate the catalyst by inducing fundamental changes in the physical structure. Oxidation is normally carried out at temperatures between about 700 and 1,200 B, using dilute oxygen-containing gases as for example, flue gases or nitrogen containing about 0.2 to by volume of oxygen. Oxidation is normally complete under these conditions in from about 1 to 30 hours.

Following oxidation, the steam-hydrogen reduction step is then carried out by flowing a stream of hydrogen and steamoverthe .catalyst at temperatures ranging between about 300 F. and 1,200 F.,.preferably between about 500 and 900 F. Normally, the treatment is carried out at atmospheric pressures, but either subatmospheric or superatmospheric pressures may be utilized. Any amount of steam added to the hydrogen stream will effect some improvement in the resulting activity, but normally about 1 to 30 mol-percent of steam in the hydr'ogenstream is used. However, it is contemplated that amounts as low as 0.5 mol-percent and as high as 90 mol-percent may also be used. Normally, the desired reduction is complete within about 0.5 to 20 hours, depending upon the catalyst used and the severity of treatment, as well as the water content of the hydrogen stream.

The following example is cited to illustrate the results obtainable in the practice of my invention, but this example is not to be construed as lirnitingin scope.-

Example :I

A fresh hydrocracking catalyst containing about 20% nickel, 21% silica, 23% titania, and 36% zirconia is first reduced with dry hydrogen at7;00 F. for 2 hours, and then utilized for hydrocracking acoker distillate gasoil boilingbetween about 400 and 600 F., thehydrocracking being. carried out at 1,500 p.s.i.g., 743 F., 4.5 LHSV, and 8,000 s.c'.f. ofhydrogen per barrel .of feed. Under these conditions, a 56 volume percent conversion to gasoline is obtained initially. As the run progresses, the catalyst gradually declines in activity, until after about 60 hours only about 30% conversion to gasoline is obtained. At this point the run is terminated, and the catalyst regenerated .by combustionwitha flue-gas-air mixture containing about 1.0% oxygen at 850 F. for 24 hours.

To compare the conve'ntionalhydrogen reduction technique with-the wet hydrogen reduction of this invention, aportion of the catalyst regenerated as described above was reduced in a dry hydrogenstream at temperatures rising gradually'from 100 to 700 F. for hours. Upon .testing the thus-treated catalyst for hydrocracking'. activity under the same conditions given above, the conversion to gasoline was only 45 volume. percent.

Another portion of the oxidized catalyst, after a pretreatment with dry hydrogen, was then subjected to a treatment wih ahydrogenstream containing 10 mol-percent of water for 3 hours at 800 Following this treatment, the catalyst was again treated with dry hydrogen stream for 5 hours at 800 to 700 F., to strip off any adsorbed water. Upon" testing this'regenerated catalyst'forhydrocracking activity under the same conditions, a 56% conversion to gasoline was obtained, thus demonstrating that the fresh activity of the catalyst is restored by the regeneration process of this invention.

It should be noted that in theforegoing runs, the hydrogen treatments were in all cases exhaustive as demonstrated by many previous runs showing that the effect of hydrogen is essentially complete after about 1 to 2 hours at 700 F. Hence, even though the duration of the total hydrogen treatment in the various runs was different, this is not a significant variable. The significant variable is deemed to be the presence of steam in the reduction gas.

Substantially similar differential results are obtained when other hydrocracking catalysts such as nickel deposited on silica-alumina are treated as in the foregoing example. It is therefore not intended that the invention should be limited to the details of the example, but broadly as defined in the following claims.

I claim:

1. A process for hydrocracking a distillate hydrocarbon feedstock boiling between about 400 and 1,000" F. to produce therefrom gasoline-boiling-range hydrocarbons, which comprises: contacting said feedstock plus added hydrogen with a regenerated hydrocracking catalyst under hydrocracking conditions including a temperature between about 400 and 900 F. and a pressure between about 500 and 5,000 p.s.i.g., saidhydrocracking catalyst having been previously utilized forhydrocracking to a point of substantial deactivation thereof, and having been then regenerated by controlled oxidation to combust carbonaceous deposits therefrom, and then subjected to a reduction treatment for about.0.5-20 hours with a stream consisting essentially of hydrogen containing a substantial proportion betweenabout 0.5 and mol-percent, of steam at temperatures between about 300 and 1,200 E, said catalyst consisting essentially of cracking component containing about 20-90% by weightof silica, and a hydrogenating component from theclass consisting of nickel and cobalt.

2. A procesas defined in claim .1 wherein sid hydrocarbon feedstock contains less than about 10 parts per million of nitrogen in the form of basic nitrogen com pounds.

3. A process as defined in claim 1 wherein said hydrocracking catalyst is essentiallynickel deposited upon a silica-alumina cracking base containing between about 50% and 90% silica.

4. A process as definedin claim'l wherein said catalyst is essentially nickel-distributed on a cracking base composed of silica, titania, and zirconia in intimate admixture.

5. A process as defined in. claim '1 wherein the steamhydrogen mixture'employed in said reduction treatment comprises between about 1 and 30 mole-percent of steam.

Hanson "Nov. 3, 1959 

1. A PROCESS FOR HYDROCRACKING A DISTILLATE HYDROCARBON FEEDSTOCK BOILING BETWEEN ABOUT 400* AND 1,000*F. TO PRODUCE THEREFROM GASOLINE-BOILING-RANGE HYDROCARBONS, WHICH COMPRISES: CONTACTING SAID FEEDSTOCK PLUS ADDED HYDROGEN WITH A REGENERATED HYDROCRACKING CATALYST UNDER HYDROCRACKING CONDITIONS INCLUDING A TEMPERATURE BETWEEN ABOUT 400* AND 900*F. AND A PRESSURE BETWEEN ABOUT 500 AND 5,000 P.S.I.G., SAID HYDROCRACKING CATALYST HAVING BEEN PREVIOUSLY UTILIZED FOR HYDROCRACKING TO A POINT OF SUBSTANTIAL DEACTIVATION THEREOF, AND HAVING BEEN THEN REGENERATED BY CONTROLLED OXIDATION TO COMBUST CARBONACEOUS DEPOSITS THEREFROM, AND THEN SUBJECTED TO A REDUCTION TREATMENT FOR ABOUT 0.5-20 HOURS WITH A STREAM CONSISTING ESSENTIALLY OF HYDROGEN CONTAINING A SUBSTANTIAL PROPORTION BETWEEN ABOUT 0.5 AND 90 MOL-PERCENT, OF STEAM AT TEMPERATURES BETWEEN ABOUT 300* AND 1,200*F., SAID CATALYST CONSISTING ESSENTIALLY OF CRACKING COMPONENT CONTAINING ABOUT 20-90% BY WEIGHT OF SILICA, AND A HYDROGENATING COMPONENT FROM THE CLASS CONSISTING OF NICKEL AND COBALT. 